If you play this game with a Xbox360-Gamepad you simply hold the Left Button "LB" and pull the left analog stick left or right while in air and spin begins.

With keyboard i think you should hold strg/ctrl and left or right for Spins. But dont know it sure.

For Twists and Flips you dont hold the Left Button and pull the Stick front or back for Flips and left and right for Twists while in air.

I made this little guide because i see the rarest Achievements in this game are for the spins.
And it takes me 3 or 4 hours gametime to find out how to do spins for myself.

Sorry for the bad english its not my native language.

Have Fun ;)